Not true...

The main hubs that level 1 players can be are Ul'dah, Limsa Lominsa and Gridania. And these are filled with players. On most worlds, Limsa is especially populated, but so is Gridania and on worlds like Balmung, Ul'dah is as well.

They all have Seasonal Events regularly, as well as getting things like job quests added to them, moogle tome exchange items, etc.

The latest two city states for a given expansion are also usually quite populated. Currently these are Solution Nine and Tuliyollal. They have new quests added to them regular in patches and their merchants get new things to be exchanged for, such as the hunt reward exchange in Tuliyollal or the tomestone exchange in Solution Nine.

The only way we'd "cut it down to 1" is to destroy Eorzea and its lore so that there is only 1. For players that have beat the MSQ, it's important that they have a change of scenery every few years at max. It would get boring if Mor Dhona was still the main tomestone hub after 11 years.